NEW YORK - Google Inc. comes in at No. 1 on the 11th annual BusinessWeek ranking of the best performing U.S. companies. Using the same mastery of algorithms that enabled it to dominate Internet search, Google launched innovative new services including one brokering advertising for traditional media.

What BusinessWeek 50 companies share is an unshakable passion for excellence. The Class of 2007 is chock full of companies that are rewriting the rules of engagement in their industries. They are the agitators, the pioneers, and the game changers that are leading the way in the 21st century. If there's one common trait among them, it's the degree to which these companies don't take their success for granted. Truth is, many work hard to anticipate and head off potential problems well before outsiders are even aware of these looming challenges.

This year's BW50 includes a number of energy companies that are basking in the sharp rise in oil prices over the past two years: Sunoco (No. 6), EOG Resources (No. 20), Valero Energy (No. 36), and XTO Energy (No. 49). And the housing boom taking place in recent years helped give a lift to a number of companies on the list, including Bed Bath & Beyond (No. 15), Sherwin-Williams (No. 22), and even Moody's (No. 29), which has enjoyed a booming business providing credit ratings for the trillions of dollars of mortgage-backed securities issued by Wall Street.

The rankings also include dynamic companies such as Nucor (No. 4), which has deployed technology and cutting-edge employee-incentive programs to stand the steel industry on its head, and Apple (No. 34), which is trying to revolutionize cell phones in the same way it did music players. Our screening also produced the names of smaller companies playing at the top of their game, such as Rockwell Collins Inc. (No. 24) and Varian Medical Systems Inc. (No. 14). They're joined by outfits ranging from Best Buy (No. 32) to payroll manager Paychex (No. 40) to Black & Decker (No. 45).

The companies in the BW50 represent BusinessWeek's choices as the "best in class" from each of the 10 sectors that make up the S&P 500. To select this year's star performers, BusinessWeek first ran companies through a proprietary screen that was refined this year to emphasize two measures -- how well each company's management has been using the capital at its disposal and sales growth. Only the best performers from each sector were chosen to ensure that the BW50 was rewarding true management excellence and not just the ability to ride the wake of a hot sector. And to provide the wisdom, perspective, and common sense that computers can't, BusinessWeek's editors and reporters reviewed each company on the list, making a limited number of changes where necessary.

The 11th annual BW50 is featured in the March 26th issue of BusinessWeek, on newsstands March 16th. Expanded content, including the full methodology, podcasts, and company profiles, can be found online.